In an image forming apparatus capable of emitting light to a document to read and copy an image from a quantity of light reflected from the document, an image forming apparatus is known that is capable of copying a high-quality image even in the case of a low quantity of light reflected from the document.
For example, JP-A-11-046289 discloses a configuration as follows: When the quantity of light from a fluorescent lamp emitting light to a document is stable after a device is switched on, the device starts to read the document and the quantity of light is corrected prior to reading a next document in order to absorb a reduced quantity of light on reading many documents by an automatic document feeder.
In the configuration of JP-A-11-046289, if the quantity of light from a fluorescent lamp is above a minimum age guarantee level, gain/shading correction is conducted to correct the variation in quantity of light. On the other hand, if the quantity of light from the fluorescent lamp is below the minimum image guarantee level, only the gain/shading correction will result in a deteriorated quality of images which have been read. Therefore, prior to the gain/shading correction, the quantity of light from the lamp itself is corrected to prevent the deteriorated quality of images.
In the configuration disclosed in JP-A-11-046289, immediately after the power source of the device is switched on, the quantity of light from a fluorescent lamp is only adjusted, and images of documents are not read before the quantity of light becomes stable. Thus, it is difficult to start reading images until the quantity of light from the fluorescent lamp becomes stable (maximum output), and a user has to wait until then.